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This patch reduces code size for all AVX targets and increases speed for some chips. SSE 4.1 introduced the useless (see code comments) 2-register form of BLENDV and only in the packed float/double flavors. AVX subsequently made the instruction useful by adding a 4-register operand form. So we just need to paper over the lack of scalar forms of this instruction, complicate the code to choose float or double forms, and use blendv on scalars since all FP is in xmm registers anyway. This gives us an approximately 50% speed up for a blendv microbenchmark sequence on SandyBridge and Haswell: blendv : 29.73 cycles/iter logic : 43.15 cycles/iter No new test cases with this patch because: 1. fast-isel-select-sse.ll tests the positive side for regular X86 lowering and fast-isel 2. sse-minmax.ll and fp-select-cmp-and.ll confirm that we're not firing for scalar selects without AVX 3. fp-select-cmp-and.ll and logical-load-fold.ll confirm that we're not firing for scalar selects with constants. http://llvm.org/bugs/show_bug.cgi?id=22483 Differential Revision: http://reviews.llvm.org/D8063 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231408 91177308-0d34-0410-b5e6-96231b3b80d8
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